Current methods for functional imaging of the human brain do not record neural activity directly, but instead measure metabolic activity consequent to neural activity. In contrast, much of our understanding of the function of the human brain comes from electrophysiological studies in animals that allow direct access to the neural signals underlying cognitive function. It is difficult to bridge the gap between neural and metabolic activity; their interrelationship is quite complex and depends on several biological and experimental factors. We propose to investigate the relationship between neural, metabolic and hemodynamic processes by use of a novel multispectral probe that allows simultaneous measurement of neural, metabolic and hemodynamic signals: spiking activity from multiple isolated single cells, local field potentials, EEG, local perfused 02 and local blood flow. This system will be used to quantify and characterize the relationship between neurophysiological and metabolic measures in an awake behaving animal model of human cognitive function. Subsequent experiments will use the multispectral probe to investigate neural, metabolic and hemodynamic signals in basic studies of visual function. A multispectral probe that is flexible and cheap enough to be integrated with daily neurophysiological recordings will enable a wide range of neurophysiologists to routinely make simultaneous measurements of neural, metabolic and hemodynamic activity. Information gained by the routine use of such a probe by the wider neurophysiological community could have dramatic effects on our interpretation and understanding of data acquired in neuroimaging experiments.